1. Field of the Invention
The present invention relates to conductive resin composite suitable for use in molding conductive articles.
2. Description of the Prior Art
With advance of electronic technology, there exists a strong demand for conductive resin composite material composed of carbon particles or carbon fiber and plastic or rubber which is light in weight, high in strength, high in conductivity, and excellent in moldability, as material for shielding static electricity or electromagnetic wave.
In the conductive resin composite material, however, since it is necessary to add a great quantity of carbon particles such as carbon black in order to reduce the resistance thereof, there exists a problem in that the viscosity of the resin material increases and therefore the moldability is deteriorated markedly. Further, there exists another problem in that the electric resistivity changes because the carbon black structure is destroyed by shearing force generated when the resin is mixed with carbon black or is molded into any given shape, and therefore it is difficult to obtain a stable electric resistivity. Further, in conductive resin composite material including carbon fiber obtained by carbonizing organic material fiber such as polyacrylonitrile and further by graphiting it, since the conductivity of the carbon fiber itself is insufficient, it is impossible to obtain a desired conductivity.
On the other hand, it has been known that resin composite low in resistivity and excellent in moldability can be obtained by adding gaseous phase growth carbon fiber (manufactured by introducing hydrocarbon and specific organic metal compound or these together with carrier gas into a reaction area, by thermodecomposing the hydrocarbon and by heat-treating it where necessary) to rubber plastic (Japanese Patent Kokai No. 61-218661). In this resin composite, however, since a large quantity of carbon fiber must be added to the resin to obtain a low resistivity resin, the moldability is deteriorated.
Further, it has been well known that the intercalation compound of graphite of gaseous phase growth carbon fiber and nitric acid or bromine is excellent in conductivity. Therefore, it has also been known that resin composite low in resistivity and excellent in moldability can be obtained by adding the above-mentioned intercalation compound to rubber or plastic (Japanese Patent Kokai Nos. 1-101372 or 1-185368). In these intercalation compound, however, there still exist other problems in that the heat resistance and therefore the heat stability are insufficient, so that the resin composite is decomposed in molding process to corrode the molding die.